Effect of corrosion protection of sol enhanced cooperating coatings on sintered NdFeB permanent magnets

In this paper, a cooperating coating (CC) was prepared on a sintered NdFeB magnet by a new technological process which is economical, operationally simple and has wider potential practicability in industrial environment. The surface morphologies and chemical composition of the coatings were investigated in detail using environmental scanning electron microscopy and energy dispersive spectroscopy (EDS) respectively. Electrochemical impedance spectroscopy and potentiodynamic polarisation tests were employed to investigate the corrosion resistance of sintered NdFeB magnet coated with CC in 0.5 M Na2SO4 solutions, which was chosen to simulate the effect of industrial environment. In order to research the long term anticorrosive properties of CC, a long term immersion test was also carried out. The results of corrosion tests showed that the CC could not only provide excellent short term but also long term corrosion protection for sintered NdFeB magnets.